Hello,
you will need the hardware and the software to do it, and it will cost you from few euros (depending on what do you already have) to hundreds of €. A cheap way is using Speaker Workshop as software and your computer sound card as hardware: check my site to have a better idea; be aware that it isn't a P'n'P solution, you need to spend time to achieve a sufficient knowledge. Expensive (but ready to go) solutions are Clio and MLLSA; with an oscilloscope you can get some measurements too.

Timn8ter, thanks for the book title. That looks like it would be something manageable.. Also, (to everyone) is it necessary to measure the frequency response and parameters of a speaker? Many companies seem to supply it, so what exactly is it used for? Does it have to do with building the crossover? Maybe after you design a crossover you do a frequency response test to see how flat the system came out or something?? tia

Originally posted by bonsai171 Timn8ter, thanks for the book title. That looks like it would be something manageable.. Also, (to everyone) is it necessary to measure the frequency response and parameters of a speaker? Many companies seem to supply it, so what exactly is it used for? Does it have to do with building the crossover? Maybe after you design a crossover you do a frequency response test to see how flat the system came out or something?? tia

Once you have the drivers in your hands, and after you've measured the Thiel&Small parameters of at least the woofers, you are ready to start designing a crossover. Now that you can plainly see the discrepancies between the published specs and actual measured specs, you can be glad you haven't built the crossovers yet.

Would say pick up a copy of Great Sound Stereo Speaker Manual by David Weems first and read it thoroughly. It is really a good book to start with (one of the best IMHO) and also fun to read. It will make a lot of things clear. After then you can decide if you really need to invest in measurement stuff. IMHO measurement is not the first thing you need when you want to DIY loudspeakers.